A technique to fractionate peripheral nerve into myelin axolemma-enriched and axonal fractions will be refined so that homogenous fractions of known enzymatic composition can be obtained. The lipid and protein composition of these subcellular fractions will be determined. A Schwann cell plasma membrane fraction will be isolated from cultured Schwann cells so that the location of these membranes in the fractionated PNS nerve can be determined. Membrane fractions from peripheral nerve will be used to stimulate the differentiation of cultured Schwann cells as judged by their ability to synthesize myelin specific proteins. Finally, the mitogenic factor found in the axolemma-enriched fraction of peripheral nerve will be solubilized and purified.